Functionally Graded Coatings and Claddings for Corrosion and High Temperature Protection

ABSTRACT

The present disclosure describes functionally graded coatings and claddings for corrosion and high temperature protection.

This application claims the benefit of U.S. Provisional Application No. 61/186,057, filed Jun. 11, 2009, tilted Functionally Graded Coatings and Claddings for Corrosion and High Temperature Protection, incorporates herein by reference in its entirety.

A process for depositing functionally graded materials and structures is described for manufacturing materials that possess the high temperature and corrosion resistant performance of ceramics and glasses, while at the same time eliminating the common mismatches encountered when these are applied to structural metal or composite substrates. An example of the structure of a functionally graded coating is shown in FIG. 1. An example of the functionally graded coating structure applied to a pipe is shown in FIG. 2.

Electrolytic deposition describes the deposition of metal coatings onto metal or other conductive substrates and can be used to deposit metal and ceramic materials via electrolytic and electrophoretic methods. Electrodeposition which is a low-cost method for forming a dense coating on any conductive substrate and which can be used to deposit organic primer (i.e. “E-coat” technology) and ceramic coatings.

The embodiments described herein include methods and materials utilized in manufacturing functionally graded coatings or claddings for at least one of corrosion, tribological and high temperature protection of an underlying substrate. The technology described herein also is directed to articles which include a wear resistant, corrosion resistant and/or high temperature resistant coating including a functionally-graded matrix.

One embodiment provides a method which will allow for the controlled growth of a functionally-graded matrix of metal and polymer or metal and ceramic on the surface of a substrate, which can corrode, or otherwise degrade, such as a metal.

Another embodiment provides a method which includes the electrophoretic deposition of controlled ratios of ceramic pre-polymer and atomic-scale expansion agents to form a ceramic (following pyrolysis). This form of electrophoretic deposition may then be coupled with electrolytic deposition to form a hybrid structure that is functionally graded and changes in concentration from metal (electrolytically deposited) to ceramic, polymer or glass (electrophoretically deposited).

Embodiments of the methods described here provide a high-density, corrosion and/or heat resistant material (e.g., ceramic, glass, polymer) that is deposited onto the surface of a substrate to form a functionally-graded polymer:metal, ceramic:metal, or glass:metal coating. The result is a coating, of controlled density, composition, hardness, thermal conductivity, wear resistance and/or corrosion resistance, that has been grown directly onto a surface.

The functionally-graded coating made according to the methods disclosed herein may be resistant to spallation due to mismatch in any of: coefficient of thermal expansion, hardness, ductility, toughness, elasticity or other property (together “Interface Property”), between the substrate and the ceramic, polymer, pre-ceramic polymer (with or without fillers) or glass (together “Inert Phase”) as the coating incorporates a material at the substrate interface, which more closely matches the Interface Property of the substrate.

In general, coatings made according to methods described herein are resistant to wear, corrosion and/or heat due to the hard, abrasion-resistant, non-reactive and/or heat-stable nature of the Inert Phase.

Polymer-derived ceramics that incorporate active fillers (e.g., TiN, Ti disilicide, and others) to improve density, have shown promise as a way to process a variety of Inert Phases, which are more dense than polymer-derived ceramics which do not incorporate these fillers. Polymer-derived ceramic composites have been demonstrated for applications, including—oxidation resistance and thermal barriers, due to their high density and low open-pore volume (e.g., the ceramic has less than 1, 5, 10, 20, 30, 40, or 50 percent voids based on volume). See, J D Toney and R K Bordia, Journal of European Ceramic Society 28 (2008) 253-257. These polymer-derived ceramics can be electrophoretically deposited. Electrophoretic deposition is a two-step process. In a first step, particles suspended in a liquid are forced to move towards one of the electrodes by applying an electric field to the suspension (electrophoresis). In a second step (deposition), the particles collect at one of the electrodes and form a coherent deposit on it. Since the local composition of the deposit is directly related to the concentration and composition of the suspension at the moment of deposition, the electrophoretic process allows continuous processing of functionally graded materials. Polymer-derived ceramics is the method used in commercial production of Nicalon® and Tyranno fibers.

In embodiments, the technology of this disclosure includes the use of electrochemical deposition processes to produce composition-controlled functionally-graded coating through chemical and electrochemical control of the initial suspension. This deposition process is referred to as Layered Electrophoretic and Faradaic Deposition (LEAF). By controlling the composition and current evolution during the deposition process, LEAF affords the means to engineer step-graded and continuously graded compositions; see Figs. and reference graphs that show dependence of Ni and Si as a function of solution chemistry and current density. Control of current evolution and direction of the electric field also offers the possibility to orient anisotropic powders allowing intimate control of both the density AND the morphology of the Inert Phase (e.g., the content and organization of added ceramic, polymer or glass materials incorporated into an electrodeposited functionally-graded coating). For example, in one embodiment by controlling current evolution and the direction of the electric field in a solution including pre-ceramic polymer, the resulting density of ceramic can be varied through the coatings to produce a varying morphology of ceramic/metal composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a functionally graded material.

FIG. 2 is an illustration of a pipe based on functionally graded material shown in FIG. 1.

FIG. 3 is graph illustrating mass loss of a substrate per area over time for several materials exposed to concentrated sulfuric acid at 200 degrees C.

FIG. 4 illustrates Active Filler Controlled Pyrolysis.

FIG. 5 illustrates LEAF electrophoretic deposition process on a fiber mat.

FIG. 6 illustrates the concentration of Si and nickel in deposits found by changing the current density. Si is the left most member of each bar graph pair and nickel the right most member of each bar graph pair measured at a specific current density

FIG. 7 illustrates the concentration of Ni in the emulsion increases from left to right. Si is the left most member of each bar graph pair and nickel the right most member of each bar graph pair prepared with the noted solution concentration of nickel.

DETAILED DESCRIPTION

Polymer-derived ceramics have shown promise as a novel way to process low-dimensional ceramics, including matrices, fibers and coatings. Polymer-derived ceramic composites have been demonstrated for applications including oxidation barriers, due to their high density and low open-pore volume. See, Torrey and R K Bordia, Journal of European Ceramic Society 28 (2008) 253-257.

The Active Filler Controlled Pyrolysis (AFCoP), polymer-derived ceramics offer many benefits over tradition ceramic processing methods including:

-   -   Liquid form with low crosslinking temperature     -   High purity reactants     -   Tailorable composition, microstructure, nanostructures and         properties     -   Ability to produce crystalline and beta-SiC phases

Pure polymer-derived ceramics suffer from certain performance limitations. One such limitation is the occurrence of volume shrinkage—up to 50%, upon sintering. To prevent this, and in order to increase the density of PDC matrices, the AFCoP process is employed, as shown in FIG. 4.

To produce fully-dense ceramic matrices, the active-filler additive can be occluded into the liquid polymer prior to casting and sintering. During sintering, this additive acts as an expansion agent, resulting in a fully dense part with near zero volume loss (e.g., there are no voids present). Active fillers include Si, Al, Ti and other metals, which on pyrolysis form SiC, Al2O₃ or TiSi₂, for example. One of the limitations of this process, as it is practiced currently, is the limited reactivity of the fillers. In many cases, due to kinetic limitations, even for the finest available powders, the filler conversion is incomplete. As will be shown in the processes described herein, the reactive “filler” and the polymer will mixed at molecular scale leading to highly efficient conversion of the filler to the product phase.

Polymer-derived ceramics and in particular, AFCoP ceramics, have shown promise as a novel way to process a variety of ceramics forms, including matrices, fibers and coatings. Polymer-derived ceramic composites have been demonstrated for applications, including-oxidation resistance and thermal barriers, due to their high density and low open-pore volume. See, J D Torrey and R K Bordia, Journal of European Ceramic Society 28 (2008) 253-257. In the some embodiments of this disclosure the AFCoP concept and the LEAF deposition process are combined to enable a manufacturing capability which can produce tailorable, low-cost, ultra-high-performance SiC_(f)/SiC composites and parts.

The Layered Electrophoretic And Faradaic (LEAF) production process employed herein enables the low-cost production of tailored ceramic matrices. A schematic of one embodiment of that process described in Scheme A.

Starting from SiC powders and fiber, a first portion of the LEAF process consists in depositing either direct SiC powders, pre-ceramic polymer emulsions (including active fillers) or a combination of these onto the SiC fiber. Electrophoretic deposition is a two-step process. In a first step, particles suspended in a liquid are forced to move towards one of the electrodes by applying an electric field to the suspension (electrophoresis). In a second step (deposition), the particles collect at one of the electrodes and form a coherent deposit on it. Since the local composition of the deposit is directly related to the concentration and composition of the suspension at the moment of deposition, the electrophoretic process allows continuous continuous processing of functionally graded materials.

A variety of substrates may be employed to prepare the compositions described herein. In one embodiment, the compositions are prepared by the LEAF electrophoretic deposition process outlined above on fiber mat as illustrated in FIG. 5.

The LEAF process offers the ability to reliably produce composition-controlled “green” (not yet sintered) ceramic through chemical and electrochemical control of the initial suspension. By shaping the starting fiber, which serves as a mandrel, LEAF provides a means to manufacture free standing parts of complex geometry, and hybrid, strength-tailored materials.

By controlling the composition and current evolution during deposition process, LEAF affords the means to engineer step-graded and continuously graded compositions. Control of current evolution and direction of the electric field also offers the possibility to orient anisotropic powders allowing intimate control of both the density AND the morphology of the ceramic deposit.

Layer thickness can be controlled by, among other things, the application of current in the electrodeposition process. In some embodiments current density may be varied within the range between 0.5 and 2000 mA/cm². Other ranges for current densities are also possible, for example, a current density may be varied within the range between: about 1 and 20 mA/cm²; about 5 and 50 mA/cm²; about 30 and 70 mA/cm²; 0.5 and 500 mA/cm²; 100 and 2000 mA/cm²; greater than about 500 mA/cm²; and about 15 and 40 mA/cm² base on the surface area of the substrate or mandrel to be coated. In some embodiments the frequency of the wave forms may be from about 0.01 Hz to about 50 Hz. In other embodiments the frequency can be from: about 0.5 to about 10 Hz; 0.02 to about 1 Hz or from about 2 to 20 Hz; or from about 1 to about 5 Hz.

In some embodiments the electrical potential employed to prepare the coatings is in the range of 5V and 5000 V. In other embodiments the electrical potential is within a range selected from 5 and 200 V; about 50 and 500 V; about 100 and 1000 V; 250 and 2500 V; 500 and 3000 V; 1,000 and 4,000 V; and 2000 and 5000 V.

In addition to direct electrophoretic deposition of SiC pre-polymers onto SiC fibers, studies have also demonstrated the co-deposition of densification additives. This is similar to the AFCoP process described above. These active-filler additives allow low-temperature densification without any detrimental effects on the fibers, as many densification additives can be sintered well below the re-crystallization temperature of the SiC_(f). See, A. R. Boccaccini et al., Journal of European Ceramic Society 17 (1997) 1545-1550. By combining these additives into the LEAF process, it is possible to produce high density and density graded ceramic matrices.

Density gradation allows for the design and development of a highly optimized SiC-fiber:SiC-matrix interface. Density gradation provides a means for balancing the optimization of the interface strength, while still maintaining a high density, and in some embodiments gas impermeable and hermetically sealed matrix. Gas impermeability is especially important in corrosion protection where a high level of gas diffusion through the coating may result in substrate attack. The LEAF process enables control and gradation of density such that a high density region near the substrate may protect the substrate from attack while a low density region near the surface may reduce the thermal conductivity of the coating.

It is believed to be possible to join non oxide ceramics using preceramic polymers with active fillers based on the work of Borida. See, J D Toney and R K Bordia, Journal of European Ceramic Society 28 (2008) 253-257. In regard to the embodiments described herein, refinement of the microstructure of ceramics joined by the LEAF processes leads to higher bond strengths In one embodiment of the technology, a sample composition can be controlled by controlling the voltage. Specifically, by slowly transitioning from a low voltage electrolytic deposition regime to a high voltage electrophoretic deposition regime it may be possible to create a functionally-graded material that gradually changes from metal to ceramic or polymer. The same could be achieved by controlling the current to selectively deposit ionic (metal) species and/or charged particle (Inert Phase) species. To create a metal:ceramic functionally graded SiC composite material would significantly increase the corrosion-resistance, wear-resistance, toughness, durability and temperature stability of a ceramic-coated structure.

In another embodiment, the coating composition can be functionally-graded by modifying the metal concentration in the electrolyte solution during electrochemical deposition. This approach affords an additional means to control the composition of the functionally-graded coating, and allows for deposition to occur at relatively lower current densities and voltages, which produced a better quality in the deposited composites. The standard cathodic emulsion system, where the emulsion particles comprise polymer, pre-ceramic polymer, ceramic or a combination thereof, can be adjusted by adding increasing amounts of nickel to the solution. This embodiment is described in Example #3.

In other embodiments, this disclosure provides a corrosion resistant coating, which changes in composition throughout its depth, from a high metal concentration at the interface with the substrate to which it is applied to an Inert Phase at the surface.

In another embodiment, the present disclosure provides a heat resistant coating, which changes in composition throughout its depth, from a high metal concentration at the interface with the substrate to which it is applied to an Inert Phase at the surface.

As used herein “Inert Phase” means any polymer, ceramic, pre-ceramic polymer (with or without fillers) or glass, which can be electrophoretically deposited. This Inert Phase may include Al₂O₃, SiO₂, TiN, BN, Fe₂O₃, MgO, and TiO₂, SiC, TiO, TiN, silane polymers, polyhydriromethylsilazane and others.

In some embodiments, ceramic particles may include of one or more metal oxides that can be selected from Zr_(x)O_(x), YtO_(x), Al_(x)O_(x), SiO_(x), Fe_(x)O_(x), TiO_(x), MgO where x=1-4, and include mixed metal oxides with the structure M_(x)Y, where M is a metal and Y is Zr_(x)O_(x), YtO_(x), Al_(x)O_(x), SiO_(x), Fe_(x)O_(x), TiO_(x), MgO. In another embodiment, M is selected from Li, Sr, La, W, Ta, Hf, Cr, Ca, Na, Al, Ti, Zr, Cs, Ru, and Pb.

As used herein, “metal” means any metal, metal alloy or other composite containing a metal. These metals may comprise one or more of Ni, Zn, Fe, Cu, Au, Ag, Pd, Sn, Mn, Co, Pb, Al, Ti, Mg and Cr. In embodiments where metals are deposited, the percentage of each metal may independently be selected. Individual metals may be present at about 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 99, 99.9, 99.99, 99.999 or 100 percent of the electrodeposited species/composition.

In other embodiments, the coating can have a coating thickness that varies according to properties of the material that is to be protected by the coating, or according to the environment that the coating is subjected to. In some embodiments, the coating can range from 0.2 and 250 millimeters, and in other embodiments the range can vary from 0.2 to 25 millimeters, 25 to 250 millimeters, or be greater than about 25 millimeter and less than about 250 millimeters. In still other embodiments, the coating thickness can range from 0.5 to 5 millimeters, 1 to 10 millimeters, 5 to 15 millimeters, 10 to 20 millimeters, and 15 to 25 millimeters. In still other embodiments, the overall thickness of the functionally-graded coating can vary greatly as, for example, between 2 micron and 6.5 millimeters or more. In some embodiments the overall thickness of the functionally-graded coating can also be between 2 nanometers and 10,000 nanometers, 4 nanometers and 400 nanometers, 50 nanometers and 500 nanometers, 100 nanometers and 1,000 nanometers, 1 micron to 10 microns, 5 microns to 50 microns, 20 microns to 200 microns, 200 microns to 2 millimeters (mm), 400 microns to 4 mm, 200 microns to 5 mm, 1 mm to 6.5 mm, 5 mm to 12.5 mm, 10 mm to 20 mm, 15 mm to 30 mm.

The functionally graded coatings described herein are suitable for coating a variety of substrates that are susceptible to wear and corrosion. In one embodiment the substrates are particularly suited for coating substrates made of materials that can corrode and wear such as iron, steel, aluminum, nickel, cobalt, iron, manganese, copper, titanium, alloys thereof, reinforced composites and the like.

The functionally graded coatings described herein may be employed to protect against numerous types of corrosion, including, but not limited to corrosion caused by oxidation, reduction. stress (stress corrosion), dissolution, dezincification, acid, base, sulfidation and the like.

The functionally graded coatings described herein may be employed to protect against thermal degradation. In one embodiment, the coatings will have a lower thermal conductivity than the substrates (e.g., metal surfaces) to which they are applied.

The coatings described herein may be employed to protect against numerous types of corrosion, including, but not limited to corrosion caused by oxidation, reduction. stress (stress corrosion), dissolution, dezincification, acid, base, sulfidation and the like. In one embodiment, the coatings are resistant to the action of strong mineral acid, such as sulfuric, nitric, and hydrochloric acids.

EXAMPLES Example 1

Preparation of a functionally graded coating comprising a Inert Phase and a metal formed utilizing a combination of electrolytic (faradaic) and electrophoretic deposition includes the following steps:

-   -   1. Acquire the desired substrate material and cut it to its         appropriate size     -   2. Sand the substrate on a circular sander using three steps to         achieve a 600 Grit finish         -   a. 120 Grit         -   b. 420 Grit         -   c. 600 Grit     -   3. Attrition Mill TiSi₂ powder for 10 or more hours.         -   a. Add isopropanol to the TiSi₂ powder to aid in grinding         -   b. The longer the time period the smaller the particle size         -   c. Rinse with isopropanol         -   d. Dry at 100 C for 8 hours     -   4. Mix the Pre-ceramic Polymer with the solvent         -   a. Pre-ceramic Polymer, Polyhydridomethysilazane (PHMS):             5.25 g         -   b. Add to Solvent, n-Octane: 6.25 mL         -   c. Add an electrodepositable metal species (e.g. Ni) to the             slurry         -   d. The total Volume ratio of slurry : n-Octane is 3:5     -   5. Mix TiSi₂ powder at 30% volume with PHMS from step 4 to         create slurry     -   6. Ball mill slurry for 4 hours with 200, 5/32″ diameter glass         beads     -   7. Dissolve the Ru₃(CO)₁₂ catalyst in n-Octane         -   a. Ru₃(CO)₁₂: 2.63 mg         -   b. n-Octane: 6.25 mL         -   c. Combine the mixture with the slurry     -   8. Ball mill for the entire slurry from step 7 for 30 minutes     -   9. Dip-coat the slurry onto the prepared substrate         -   a. Dip substrate into slurry         -   b. Apply a current to affect electrolytic deposition of the             metal content of the coating         -   c. Increase the current to affect electrophoretic deposition             of the ceramic content of the coating         -   d. Attach the substrate to the Instron head         -   e. Optionally dip into the substrate into the slurry and             remove it at a rate of 50 cm/min     -   10. Cross-link the samples in humid air         -   a. Hang the dipped substrates in a jar filled ⅕ with water         -   b. Temperature: 150 C         -   c. Time: 2 hours     -   11. Pyrolyze the dipped samples with flowing air         -   a. Hang the samples from a ceramic stand and place them in             the oven         -   b. Ramp rate: 2 C/min         -   c. Hold temperature: 800 C         -   d. Hold Time: 2 hours         -   e. Ramp down: 2 C/min     -   12. Remove the completed sample from the oven.

The resistance of a TiSi₂ filled and an unfilled coating to degradation by 200 degree C. concentrated sulfuric acid is shown in FIG. 3. A standard of Alloy 20 and 316 stainless steel are provide for reference. The filled coating showed the least loss of weight.

Example 2

Toughness Improvements Employing LEAF Processes To Incorporate a Low-Content of Metal Binder Into Composites

In order to improve toughness, the LEAF processes a low-content of a metal binder (e.g., nickel in this Example) may be incorporated into composites. As shown in FIG. 6, the concentration of nickel in deposits can be controlled by changing the current density employed.

Example 3

A Functionally Graded Coating

In order to create a functionally-graded coating, a standard nickel plating bath was added to the polymer emulsion in 1% increments by volume up to 10%.

Samples were subsequently exposed to a DC current for a fixed period. The bath was stirred and agitated at the conclusion of each test in order to ensure proper solution mixing and suspension.

The observations attained from the optical image of the samples were confirmed by the EDX compositional analysis. The Ni composition of the coating was increasing as the Ni concentration in solution increased. These results once again demonstrate the feasibility of creating a functionally graded ceramic:metal composite material by controlling the concentration of metal and Inert Phases in the electrolyte during the deposition process.

In addition, the data demonstrated that the silicon content in the deposit remain constant over time. This result is to be expected as a result of the voltage driven nature of electrophoretic deposition, and a constant current density and similar voltages were used for the samples. The nickel emulsion system can be optimized through concentration alteration and current and voltage modulation to create a structural material suitable for corrosion resistant, wear resistant, heat resistant and other applications.

Example 4

Nickel, a siloxane-based pre-ceramic polymer particles and ceramic SiC particles are added to an organic electrolyte Note that in this case, the polymer is not deposited as an emulsion, but rather directly as a lacquer. A cathode and an anode were connected to a power supply. The substrate was connected to the cathode and inert anodes were connected to the anode. A potential was applied across the anodes and cathode, which potential ramped from a low voltage (around 5-100V) to a high voltage (about 100-1000V). The high voltage was held for a period of time. In an SEM of the resulting structure, where gray masses are the SiC fibers the darker gray areas are a mixed matrix of SiOC and SiC. SiOC is present due to the heat treatment in an environment in which oxygen was present. The white areas are where the nickel was able to infiltrate into the cracks and reinforce the structure of the material.

The addition of the SiC filler particles into the pre-ceramic polymer led to the densification and, strengthening of the specimen by reducing shrinkage on formation. The sub-micron size of the filler particles facilitated the flow and migration of the matrix around the SiC fibers. The upper-right corner of the image contains a zoomed in view of the interface around a fiber. Any gaps present were filled and strengthened by the nickel metal deposition.

Fiber break analysis was performed on a selection of samples that contained the functionally graded metal:SiC structure to determine the toughness and fracture characteristics of various SiC bundles. The toughness of the fiber matrix can be determined through the visual inspection of fiber pull-out during fracture. This is observed in SEM images of the fracture surface of a dipped coated ceramic bundle cross-linked at 500° F. for 2 hours.

The above descriptions of embodiments of methods and compositions are illustrative of the present technology. Because of variations which will be apparent to those skilled in the art, however, the technology is not intended to be limited to the particular embodiments described above. 

1. A method for producing a functionally-graded coating, comprising: (a) exposing a mandrel or a substrate to be coated to an electrolyte containing one or more metal ions, and containing one or more ceramic particles, polymer particles, pre-ceramic polymer particles, active fillers, or a combination thereof; (b) applying an electric current and changing in time one or more of: an amplitude of the electrical current, an amplitude of an electrical potential, an electrolyte temperature, a relative concentration of metal ions or particles in the electrolyte, or an electrolyte agitation, to change a ratio of an electrodeposited species; and (c) promoting growth of the functionally-graded coating until a desired thickness of the coating is achieved, the electrodeposited species being varied throughout the desired thickness of the coating.
 2. (canceled)
 3. The method of claim 1, further comprising heat treating the coating to cause partial or complete sintering of a pre-ceramic polymer applied to said mandrel or substrate by said applying of said electric current.
 4. The method of claim 3, where the heat treating has a heat treatment temperature between 200 degrees C. to 1300 degrees C. 5-6. (canceled)
 7. The method of claim 1, wherein said one or more metal ions are selected from the group consisting of: Ni, Zn, Fe, Cu, Au, Ag, Pd, Sn, Mn, Co, Pb, Al, Ti, Mg, and Cr.
 8. The method of claim 1, wherein the ceramic particles are chosen from metal oxides, carbides, nitrides, or combinations thereof. 9-12. (canceled)
 13. The method of claim 1, wherein the polymer particles comprise one or more of: epoxy, polyurethane, polyaniline, polyethylene, poly ether ether ketone, polypropylene, and siloxane; wherein the pre-ceramic polymer particles comprise one or more of: siloxides, silences, silanes, organosilanes, siloxanes, polyhedral oligomeric silsesquioxanes, polydimethylsiloxanes, and polydiphenylsiloxanes; and/or wherein the active fillers comprise one or more of: titanium disilicide, yittrium disilicide, nickel disilicide, niobium disilicide, tantalum disilicide, vanadium disilicide, chromium disilicide, and molybdenum disilicide. 14.-24. (canceled)
 25. A coating prepared by the method of claim
 1. 26. An electrodeposited corrosion-resistant functionally-graded coating, comprising: an interior first region of metal; and an exterior second region of polymer, pre-ceramic polymer, or ceramic, wherein a non-discrete region is disposed between the first region and the second region, the non-discrete region being a combination of the first region and the second region.
 27. The functionally-graded coating of claim 26, wherein said non-discrete region has a monotonically increasing metal concentration gradient.
 28. The functionally-graded coating of claim 26, wherein said non-discrete region has a monotonically decreasing metal concentration gradient.
 29. The functionally-graded coating of claim 26, wherein said functionally-graded coating is corrosion-resistant or substantially corrosion resistant, is heat resistant or substantially heat resistant, and/or wear resistant or substantially wear resistant. 30-31. (canceled)
 32. The functionally-graded coating of claim 26, wherein said metal comprises one or more metal ions selected from the group consisting of: Ni, Zn, Fe, Cu, Au, Ag, Pd, Sn, Mn, Co, Pb, Al, Ti, Mg, and Cr.
 33. The functionally-graded coating of 26, wherein said ceramic comprises one or more metal oxides, carbides, nitrides, or combinations thereof. 34-37. (canceled)
 38. The functionally-graded coating of claim 26, wherein the polymer comprises one or more of: epoxy, polyurethane, polyaniline, polyethylene, poly ether ether ketone, polypropylene, and siloxane; and wherein the pre-ceramic polymer comprises one or more of: siloxides, silences, silanes, organosilanes, siloxanes, polyhedral oligomeric silsesquioxanes, polydimethylsiloxanes, and polydiphenylsiloxanes.
 39. (canceled)
 40. The functionally-graded coating of claim 26, further comprising a first substrate disposed proximate to a second substrate comprising iron, copper, zinc, aluminum, titanium, nickel, chromium, graphite, carbon, cobalt, lead, epoxy, or composites or alloys thereof. 